The present invention relates to the conversion of an epoxide to a substituted tetrahydrofuran by hydrogenation in the presence of an acid.
The cleavage of epoxides to make new compounds containing a hydroxyl group is in general known in the art. See, for example, Morrison & Boyd, "Organic Chemistry," 2nd Ed., at pp. 877-992.
A Kotz and K. Righter in an article in J. Prakt. Chem. [2] 111, 373 (1925) disclose hydrogenation of an epoxide to obtain a secondary alcohol, as follows: ##EQU2##
Park and Fuchs state in J. Org. Chem., January 1957, at page 93: "Only a few oxides with electron-withdrawing groups have been hydrogenated, and a secondary alcohol is always produced. Glycidol, epichlorohydrin, and butadiene dioxide are reduced to 1,2-propanediol, 1-chloro-2-propanol, and 2,3-butanediol, respectively, as the main product."
Searles and Butler in JACS, Vol. 76, p. 56 (1954), disclose reduction of 1-chloro-2,3-epoxy propane using hydrogen and a nickel catalyst. The product obtained is 1-chloro-2-propanol, that is, the epoxy group was reduced to result in the OH group being on the secondary rather than the primary carbon atom.
However, Newman, Underwood and Renoll, in JACS, Vol. 71, p. 3362 (1949) disclose reduction of 1,2-epoxy decane using a nickel catalyst to obtain primary decane alcohol.
French Pat. No. 845,305 discloses the conversion of 1,4-butylene glycol or its alkylated products to tetrahydrofurans. According to the patent, at 250.degree.-350.degree.C, or with a catalyst of alkaline nature such as Na.sub.2 PO.sub.4, even at 400.degree.-450.degree.C, one mol of water is eliminated with the resultant formation of tetrahydrofurans.